medwireNews: US researchers believe that the rising numbers of thyroid cancer cases in recent years may be due to an “epidemic of diagnosis” rather than a true increase in the incidence of the disease.

Between 1975 and 2009, the incidence of thyroid cancer increased from 4.9 to 14.3 cases per 100,000 individuals in the USA, giving a relative rate of 2.9, show data from the Surveillance, Epidemiology, and End Results program and the National Vital Statistics System.

However, this increase was not mirrored in the mortality rate for thyroid cancer, which remained stable over the same time period, at approximately 0.5 deaths per 100,000 head of population, say Louise Davies (VA Medical Center, White River Junction, Vermont, USA ) and H Gilbert Welch (Dartmouth Institute for Health Policy and Clinical Practice, Hanover, New Hampshire, USA).

Finding that the increase in diagnosis was driven by a rise in the detection of papillary thyroid cancer, which often remains asymptomatic, from 3.4 to 12.5 cases per 100,000, the authors suggest that “the time has come to address the problem of papillary thyroid cancer overdiagnosis and overtreatment”.

As expected, the incidence of thyroid cancer was higher in women than men but the rise in thyroid cancer diagnosis was four times faster in women with absolute increases of 14.9 and 3.8 cases per 100,000 over the study period, respectively.

Writing in JAMA Otolaryngology, Louise Davies and H Gilbert Welch note that 85% of patients diagnosed with thyroid cancer underwent total thyroidectomy, often with lymph node dissection, and approximately 50% of patients also received radiotherapy.

They suggest active surveillance, reclassifying small neoplasms as non-cancer and identifying patient groups at high risk could combat overdiagnosis and overtreatment in the long term.

For now, the authors recommend that physicians assess the thresholds for palpation, imaging and biopsy and openly discuss the uncertain nature of small thyroid tumours with their patients and share decision-making about treatment options.

“Patients - and in the case of thyroid cancer, particularly women - need protection not only from the harms of unnecessary treatment but also the harms of unnecessary diagnosis,” they conclude.